A Pair-Feeding Study Reveals That a Y5 Antagonist Causes Weight Loss in Diet-Induced Obese Mice by Modulating Food Intake and Energy Expenditure

ABSTRACT Neuropeptide Y (NPY) is thought to have a significant role in the physiological control of energy homeostasis. We recently reported that an NPY Y5 antagonist inhibits body weight gain in diet-induced obese (DIO) mice, with a moderate reduction in food intake. To clarify the mechanism of the antiobesity effects of the Y5 antagonist, we conducted a pair-feeding study in DIO mice. The Y5 antagonist at 100 mg/kg produced a moderate feeding suppression leading to an 18% decrease in body weight, without altering body temperature. In contrast, the pairfed group showed only a transient weight reduction and a reduced body temperature, thus indicating that the Y5 antagonist stimulates thermogenesis. The Y5 antagonist-treated mice showed an up-regulation of uncoupling protein mRNA in brown adipose tissue (BAT) and white adipose tissue (WAT), suggesting that both BAT and WAT contribute to energy expenditure. Thus, the Y5 antagonist induces its antiobesity effects by acting on both energy intake and expenditure

Discovery of Tetrasubstituted Imidazolines as Potent and Selective Neuropeptide Y Y5 Receptor Antagonists: Reduced Human Ether-a-go-go Related Gene Potassium Channel Binding Affinity and Potent Antiobesity Effect

A series of novel imidazoline derivatives was synthesized and evaluated as neuropeptide Y (NPY) Y5 receptor antagonists. Optimization of previously reported imidazoline leads, <b>1a</b> and <b>1b</b>, was attempted by introduction of substituents at the 5-position on the imidazoline ring and modification of the bis(4-fluorphenyl) moiety. A number of potent derivatives without human ether-a-go-go related gene potassium channel (hERG) activity were identified. Selected compounds, including <b>2a</b>, were shown to have excellent brain and CSF permeability. Compound <b>2a</b> displayed a suitable pharmacokinetic profile for chronic in vivo studies and potently inhibited d-Trp³⁴NPY-induced acute food intake in rats. Oral administration of <b>2a</b> resulted in a potent reduction of body weight in a diet-induced obese mouse model

A neuropeptide Y Y5 antagonist selectively ameliorates body weight gain and associated parameters in diet-induced obese mice

Neuropeptide Y (NPY) is thought to have a major role in the physiological control of energy homeostasis. Among five NPY receptors described, the NPY Y5 receptor (Y5R) is a prime candidate to mediate some of the effects of NPY on energy homeostasis, although its role in physiologically relevant rodent obesity models remains poorly defined. We examined the effect of a potent and highly selective Y5R antagonist in rodent obesity and dietary models. The Y5R antagonist selectively ameliorated diet-induced obesity (DIO) in rodents by suppressing body weight gain and adiposity while improving the DIO-associated hyperinsulinemia. The compound did not affect the body weight of lean mice fed a regular diet or genetically obese leptin receptor-deficient mice or rats, despite similarly high brain Y5R receptor occupancy. The Y5R antagonist acts in a mechanism-based manner, as the compound did not affect DIO of Y5R-deficient mice. These results indicate that Y5R is involved in the regulation and development of DIO and suggest utility for Y5R antagonists in the treatment of obesity